Have you looked..
There is a 76 Caddy 500 and TH400 sitting out in my shed for the past several years awaiting a new home--I nearly put it in my 79 C10 last year when the 250 six croaked..but I felt a 1/2 ton was a waste of all that HP and torque!(not to mention it might shred even the 12 bolt rear end!)...I'd prefer to use it in a truck that will haul heavy loads,like a ramp truck or one ton dump body truck..at the rate I'm going,it will be siezed before i get around to doing anything with it!
I know a few guys who have 500's in their C10 Chevy trucks..I rode in and drove one of them,and it was like driving a dragster!..even with 3.08 gears,the guy had NO problem BAKING the tires in all 3 gears,until we reached 80mph,when the truck finally caught up with the tires about 1/8 of a mile away!

...I thouroghly enjoyed my time behind the wheel!..
He didnt change his "mid sump" oilpan,but made taller engine mounts so it wouldn't hit the crossmember,it looks like hell,and I'm suprised it doesen't vibrate due to the extreme angle on the tranny tailshaft,but it didn't!..he used the "super long tail"TH400 like I have,and a Pontiac Lemans driveshaft fit perfectly with no alterations!---only the crossmember to the tranny mount needed to be moved,a few holes drilled,and the tranny mount needed adapting(caddy ones have a "weird" bolt pattern not shared with any other GM!)...other than that,little modification was needed..he put another truck just like it together in one weekend,after he gathered all the parts,for his friend!...
